Analysis of a long-duration hyperpolarization produced by octopamine in an identified effector neuron of Helisoma.
Recent studies have demonstrated that patterned activity in the buccal ganglion of Helisoma trivolvis can be modulated by a variety of neuroactive substances. This study examines the effect of one of these substances, octopamine, on the identified buccal neuron B5. Perfusion of B5 with octopamine produces a 10-20 mV, long-duration hyperpolarization which is associated with an increase in membrane conductance. The magnitude of the hyperpolarization is dose-dependent with a dissociation constant of approximately 5 microM. The reversal potential for the octopamine-induced hyperpolarization (-84 mV) is nearly identical to the predicted potassium equilibrium potential (-85 mV). This result, together with the results of experiments in which extracellular potassium concentrations were altered, demonstrates that octopamine modulated a potassium current in B5.
Bahls
F H
FH
Department of Physiology and Biophysics, University of Washington, Seattle 98195.
D000818:Animals; D004305:Dose-Response Relationship, Drug; D005071:Evoked Potentials / Q000187:drug effects; D005724:Ganglia / Q000502:physiology; D066298:In Vitro Techniques; D008974:Mollusca; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D009655:Octopamine / Q000494:pharmacology*; D011188:Potassium / Q000494:pharmacology
D009655:Octopamine; D011188:Potassium